How to calculate decay in premium

Suppose I open a short straddle for BNF at 44000 CE and PE.
2 days later, I need to put a condition to add a hedge if theta has decayed by 20%. Is there a keyword to retrieve the initial theta and compare with current theta of leg?

Yes. Read the theta at entry and compare it with the leg’s current theta.

Option 1: EntryTheta

EntryTheta returns the theta of the position at strategy entry. In a Repair Once condition:
Theta ( Traded Instrument Name ( Entry, instrument, NIFTY BANK, 1, 1, 1 ) ) compared with EntryTheta × Number(0.8) (built with Math Operation).

Theta of a short option is usually quoted as a negative number, so check the sign in the Notification Log before you choose <= or >=.

Option 2: your own runtime variable per leg

1. In the Entry Runtime section: theta_ce = Theta ( Traded Instrument Name ( Entry, ..., 1, 1, 1 ) ). It is written right after the entry leg is taken.
2. In Repair Once: compare the current Theta of that leg with Get Runtime Number ( theta_ce ) × 0.8.
3. In that Repair Once’s Position Builder, add the hedge legs.

Option 2 lets you track CE and PE separately.

Note: theta normally changes as expiry nears, so “decayed by 20%” may be easier to read from the premium itself: LTP ( leg ) <= Traded Instrument ( Entry, price, ... ) × 0.8.

Test in Live Offline first. Greeks keywords: Delta, Gamma, Theta, Vega, Rho, Iv. Reference: Keyword Documentation — Tradetron

Answer written with AI from Tradetron docs (Oct 2026). Original replies are kept above. Spot something wrong? Reply below.